EPA Proposes Tightened Ozone Standards

August 16, 2007
Client Alert Newsletter August 2007

On July 11, the U.S. Environmental Protection Agency ("EPA") published a proposal to tighten the National Ambient Air Quality Standard ("NAAQS") for ground-level ozone, or "smog." Despite ongoing regulatory activity to implement the 1997 NAAQS, the proposal stems from a review of the 1997 NAAQS commencing in 2000. From that review, EPA found that ozone exposure at the 1997 standard can be linked to mortality, increased asthma medication use, school absenteeism and cardiac effects.

EPA would reduce the primary (public health-based) NAAQS from the existing 8-hour level of 0.08 parts per million ("ppm") to the range of 0.070-0.075 ppm. Unlike the prior standard, EPA has also proposed an option to set a distinct secondary (public welfare-based) ozone NAAQS, at a cumulative seasonal level of 7 to 21 ppm-hours measured over 12 hours per day in a three-month period during the ozone season. This standard is designed to protect sensitive plants from repeated ozone exposure in the growing season.

The proposed revision must go through a series of actions before implementation. First, a public comment period on the proposal runs until October 9, with public hearings scheduled in the interim. EPA expects to finalize the rule in March 2008, with state attainment designation recommendations due in June 2009. EPA will finalize designations in 2010, and states will submit SIP revisions by 2013. Attainment dates, varying by nonattainment classifications, will range from 2013 to 2030.